1. Technical Field
The present invention relates in general to data communication systems and in particular to networked data communications systems. More particularly, the present invention relates to a specific mode of data communication utilizing ethernet frame transportation. Still more particularly, the present invention relates to filtering broadcast frames on an ethernet network.
2. Description of the Related Art
Ethernet communications are accomplished by transporting digital communications in frames across a network of computers or xe2x80x9cstations.xe2x80x9d A frame, the basic data transmission unit in bit oriented protocols, is a discrete group of data bits in a particular protocol, with flags to indicate a beginning and an end of the frame. The frame usually contains addressing and error checking information.
Data, that is being transmitted on an ethernet based network, is encapsulated by various network layers from the Application layer to the physical layer. As the data is received, the headers are stripped by the receiving station layers as the frame is passed from layer to layer in the receiving station. Included in the transport layer is a sequence number so that a file may be broken into multiple packets and recombined at the receiving end. The network layer provides the application to assemble datagrams into frames to be transmitted over the network to a receiving station.
On an Ethernet based network, stations are connected to a shared signaling system. All the ethernet signals are serially transmitted to every connected station. The header applied to data to be transmitted includes Medium Access Control (MAC) and consists of a preamble, destination address, source address and the data length segments of the frame.
A unique address (48 bits) is assigned to Ethernet cards as they are manufactured. As a frame is placed in the channel of an Ethernet medium, all connected Ethernet cards check the MAC for the destination address. The Ethernet card compares the destination address with the address it was manufactured with. Only the Ethernet card with the destination address will read the entire frame. All the other cards on the network will ignore the data in the frame when the other cards determine the address does not match with their manufacture installed address.
A problem with being on the Ethernet is that there are broadcasts happening all the time. At the lower levels of the ethernet hardware, all the connected cards read the broadcast. Many of the broadcasts don""t need to be accepted by most of the connected cards, because the broadcast is for a particular card. Many ethernet card designs accept all broadcast frames and then filter out any errant frames in software. Utilizing software to accept or reject frames requires processing power, which delays the station processor from other uses.
It would be desirable to determine whether or not a frame was intended for a particular station at a much lower level in the frame transmission hierarchy to reduce the load on the receiving station""s processor. If the acceptance or rejection of the frame takes place in hardware, the step of loading the frame in memory to compare the address of the frame to the address of the ethernet card may be eliminated and thus reduce processor loading.
It is therefore one object of the present invention to provide a method and system that will reduce the load on a microprocessor in a station (computer) connected to an ethernet network.
It is another object of the present invention to provide a method and apparatus for comparing frames broadcast on an ethernet network utilizing hardware.
It is yet another object of the present invention to provide a method and apparatus to filter out unwanted frames from ethernet traffic.
The foregoing objects are achieved as is now described. Within a communication node, low level hardware is programmed and provided with filter data to accept broadcast frames. A high level layer of hardware, utilizing the pre-loaded, pre-defined comparison data, checks incoming frame header information. Based on pre-defined filter data or reference values loaded into low level registers, the high-level hardware will reject or accept submitted data communication frames. This method reduces the requirement for software to operate on each incoming frame header, thus reducing load on the processor.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.